Palladium-doped graphene-modified nano-carbon ionic liquid electrode: preparation, characterization and simultaneous voltammetric determination of dopamine and uric acid

We described a nano-carbon ionic liquid electrode modified with palladium-doped graphene (Pd-GR/nano-CILE) for electrochemical analysis of dopamine (DA) and uric acid (UA). The surface morphologies of the electrodes and palladium-doped graphene (Pd-GR) were observed by scanning electron microscopy and transmission electron microscopy. Cyclic voltammetry and electrochemical impedance spectroscopy were used for investigating the electrochemical properties of the proposed sensor. The oxidation peaks of DA and UA were well separated at the Pd-GR/nano-CILE using differential pulse voltammetry. The sensor displayed good electrocatalytic activity toward DA and UA with increased peak currents and reduced peak potentials compared with conventional carbon paste electrode. Under optimal conditions, linear calibration plots for the analysis of DA and UA were obtained in the range of 5–200 μM, respectively. The detection limits (at an S/N ratio of 3) were 0.5 μM for DA and 0.8 μM for UA. The method was successfully applied to the determination of DA and UA in spiked human urine and serum samples.